Stamens are not essential as an attractant for pollinators in females of cryptically dioecious Thalictrum pubescens Pursch. (Ranunculaceae)

 It has been hypothesized that females of some dioecious species maintain stamens that produce sterile pollen as a means of attracting pollinators to promote greater seed set. However, this hypothesis has rarely been tested. This paper examines the role of pollinators in the maintenance of sterile stamens in the cryptically dioecious species, Thalictrum pubescens. Wind was found to contribute to pollination; branches of female T. pubescens enclosed in cheesecloth to exclude insects but not wind were still able to set seed. Therefore, females may not need the stamens for pollination. In 1994, insects were found to discriminate against emasculated female flowers, but this discrimination did not lead to a significant difference in either the amount of pollen received or seed set. In 1995, emasculation was combined with the addition of pollen to determine if emasculated females were pollen limited. No significant effect of pollen addition or emasculation was found. Emasculated branches in the pollen-addition treatment appeared to have slightly lower seed set than non-emasculated branches that received pollen, indicating that the slight reduction in seed set was caused by emasculation rather than pollen limitation. Since stamens do not appear to be maintained as pollinator attractants, other explanations, such as genetic constraints, must be investigated. Received: 4 February 1997 / Revision accepted: 20 May 1997     

The pollination ecology ofBletilla striata (Orchidaceae)

Anthecological observations of an orchidBletilla striata were carried out in Kobe, Japan. The purplish pink flowers were visited by 26 species of insects belonging to Hymenoptera, Diptera and Lepidoptera, although the flower did not offer food rewards of any kind. Candidates for pollination were seven species of aculeate Hymenoptera with a body size that well fitted the space in between the column and labellum. The most effective candidate was the male of the longhorn beeTetralonia nipponensis, judging from its abundance and legitimate intrafloral behavior. The female ofT. nipponensis and the other six species also contributed to promote out-crossing, but to a lesser extent than the maleT. nipponensis, since they occasionally exhibited illegitimate intrafloral behaviors for pollination and also, their flower visitation rate was lower.     

The consumption and utilization of the spiral blue-green algae Spirulina platensis in artificial diets by the silkworm, Bombyx mori

The consumption and utilization of various concentrations of the spiral blue-green algae, Spirulina platensis (Nordst.) Geitl., by the fourth-instar larvae of the silkworm, Bombyx mori L., was studied by incorporation into an artificial diet. The silkworms ingested more food on the low algal-powder diets, whereas they digested more efficiently on the high algal levels. The larvae fed on diets containing 30–40% algae had the shortest larval duration compared to those on low algal-powder diets. The freeze-dried powder of S. platensis is well utilized by B. mori larvae when added to artificial diets at levels between 15% and 30%, although the high algal content at 40% was slightly better for the efficiency of conversion of ingested diet into body substance (E.C.I.) and the cocoon production. However, analysis of the protein content in feces indicated an excess of the algal powder at 40%. Measurements of data on the food consumption and utilization in this study proposed that this spiral alga is dietetically utilizable as a protein source for rearing the silkworm in smaller quantities than on a soybean meal.

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Resúmé La consommation et l'utilisation de différentes concentrations de Spirulina platensis par les chenilles de 4ème stade de Bombyx mori, ont été étudiées par incorporation dans un aliment artificiel. Les vers à soie ont ingéré plus d'aliment avec les régimes à faible concentration en algue, tandis qu'ils ont digéré plus efficacement les régimes à haute concentration d'algue. Les chenilles alimentées sur des régimes contenant 30 à 40% d'algue ont eu un développement larvaire plus bref que celles alimentées sur des régimes à faible concentration. La poudre congelée et séchée de S. platensis incorporée aux taux de 15 à 30% dans le régime artificiel est bien utilisée par les chenilles de B. mori, quoiqu'une teneur de 40% soit légèrement meilleure pour l'efficacité de conversion de l'aliment en matière vivante (E.C.I.) et la production de cocons. Cependant, l'analyse du contenu protéique dans les excréments révélait un excès de poudre d'algue à 40%. L'analyse des données au cours de cette étude, sur la consommation et l'utilisation des aliments, montre que S. platensis est utilisable diét étiquement en plus petite quantité que la farine de soja comme source de protéines pour l'élevage du ver à soie.

     

Spatial distribution of seston in an artificially mixed system

Seston size distribution was determined with a Coulter Counter to investigate seston interaction and its effects on phytoplankton production. Spatial distribution patterns of the non-productive component of the seston were as complex as those commonly associated with algae. Seston might interact influencing production by changes in optical depth, abrasive actions and nutrient adsorption.     

COMPARISON OF ATTACHED DIATOM COMMUNITIES ON NATURAL AND ARTIFICIAL SUBSTRATES1

A study of attached diatom communities on artificial and natural substrates was conducted in Wheelwright Pond, New Hampshire, during 1975. There were differences in the species composition growing on artificial glass slides and natural substrates. The slides favored the accumulation of Achnanthes minutissima Kütz. and decreased the relative abundance of Eunotia incisa W. Sm. ex. Greg. and Cocconeis placentula v. euglypta (Ehr.) Cleve. Large growths of planktonic species were also noted on the slides. Compositional differences between slides positioned at 15–30 cm (upper) and 1 m (lower) from the surface of the water were minimal. A similar community composition of periphytic diatoms was found on five aquatic macrophytes.     

Genetic architecture of yield and components of yield in mustard (Brassica juncea (L.) Czern & Coss.)

Summary The relative ability of cross- and self-pollen to achieve fertilisation in Brassica was studied by making double pollinations using cross-pollen carrying a dominant seedling marker gene. With simultaneous self- and crosspollination 12–40% self-seed was set, but when cross-pollen was applied to the stigma four hours before self-pollen, only 2–4% self-seed was obtained. In two plants to which cross-pollen was applied at various time intervals after self-pollen there was a tendency for the percentage of self-seed to increase as the time interval increased. In a third plant this trend was not apparent, probably because of a greater degree of self-incompatibility. The competitive advantage of the first pollen to arrive on the stigma is discussed in relation to the strength of the self-incompatibility and the sib problem in F₁ hybrid brassicas.     

Species-specific aggregation factor in sponges. XIII. Entire and core structure of the large circular proteid particle from Geodia cydonium

High-molecular weight particles have been isolated from the sponge Geodica cydonium. In the "native" from these particles consist of a spherical center and have 25-30 filaments attached to it. The core structure of the particles is assembled of a central circle and 25 radially-arranged filaments. The core structure is obtained from the entire structure by incubation in a medium, containing a non-ionic detergent and EDTA. The molecular weight of the enitre structure was in the range of 1.4 X 10(9) daltons or more and of the core structure 6.1 x 10(8) daltons. Two functional proteins are released from the "native" particles: the aggregation factor and the sialytransferase.     

紫外分光光度法测定牛黄中胆酸的研究

本文研究了用紫外分光光度法测定牛黄中胆酸的实验条件和方法。